T distribution on a TI 83: How to Find it in Easy Steps

T distribution on a TI 83: Overview

The T distribution (sometimes called Student’s T) is actually a set of distributions, differentiated by the degrees of freedom (df). There’s only a slight difference between the t distribution and a normal distribution; for some situations (like a very small sample), you have to use the t-dist to find probabilities.
Take a look at a traditional textbook T table, and you’ll actually find many T tables, which can be a little overwhelming. Instead of poring over tables, you can use a TI 83 graphing calculator to assist you in finding T values.
You might be asked to find the area under a T curve, or (like Z scores), you might be given a certain area and asked to find the T score.

Finding a T-Value on the TI 83

T distribution on a TI 83: Steps

Sample problem: Find the area under a T curve with degrees of freedom 10 for P( 1 ≤ X ≤ 2 ). Use the t distribution on a TI 83.

Step 1: Press 2ndVARS5 to select tcdf(.

Step 2: Enter the lower and upper bounds, and the degrees of freedom. The lower bound is the lowest number and the upper bound is the highest number: 1,2,10)

Your screen should now read tcdf(1,2,10)

Step 3: Press ENTER. The answer is .133752549, or about 13.38%.

That’s how to find a T distribution on a TI 83!

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